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United States Patent |
5,585,743
|
Kenji
,   et al.
|
December 17, 1996
|
ECL-CMOS level conversion circuit
Abstract
In a level conversion circuit for converting a pair of first-level signals
into a pair of second-level signals, an input buffer circuit converts the
pair of first-level signals into a pair of buffered signals which vary
within a first voltage range situated below a second voltage range within
which the pair of first-level signals vary. An amplifier circuit, which
includes a plurality of CMOS differential amplifier circuits cascaded,
converts the pair of buffered signals into the pair of second-level
signals varying within a third voltage range broader than the second
voltage range of the pair of first-level signals.
Inventors:
|
Kenji; Hisashige (Kawasaki, JP);
Yokota; Noboru (Kawasaki, JP)
|
Assignee:
|
Fujitsu Limited (Kawasaki, JP)
|
Appl. No.:
|
570830 |
Filed:
|
December 12, 1995 |
Foreign Application Priority Data
Current U.S. Class: |
326/73; 326/68 |
Intern'l Class: |
H03K 019/094; H03K 019/017.5 |
Field of Search: |
307/475,451,455
326/73,68
|
References Cited
U.S. Patent Documents
4437171 | Mar., 1984 | Hudson et al. | 307/475.
|
4453095 | Jun., 1984 | Wrathall | 307/475.
|
4563601 | Jan., 1986 | Asano et al. | 307/475.
|
5075578 | Dec., 1991 | Wendell | 307/475.
|
5153465 | Oct., 1992 | Sandhu | 307/475.
|
5216298 | Jun., 1993 | Ohba et al. | 307/475.
|
5293081 | Mar., 1994 | Chiao et al. | 307/475.
|
5329183 | Jul., 1994 | Tamegaya | 307/475.
|
Foreign Patent Documents |
59-139727 | Aug., 1984 | JP.
| |
63-015519 | Jan., 1988 | JP.
| |
3-283813 | Dec., 1991 | JP.
| |
Primary Examiner: Westin; Edward P.
Assistant Examiner: Roseen; Richard
Attorney, Agent or Firm: Staas & Halsey
Parent Case Text
This application is a continuation of application Ser. No. 08/136,045,
filed Oct. 14, 1993, now abandoned.
Claims
What is claimed is:
1. A level conversion circuit for converting a pair of first-level signals
into a pair of second-level signals, said level conversion circuit being
supplied with a high-potential power supply voltage and a low-potential
power supply voltage, said level conversion circuit comprising:
input buffer means for converting the pair of first-level signals into a
pair of buffered signals which vary within a first voltage range situated
below a second voltage range within which the pair of first-level signals
vary; and
an amplifier circuit comprising a plurality of CMOS differential amplifier
circuits cascaded, the amplifier circuit converting the pair of buffered
signals into the pair of second-level signals varying within a third
voltage range broader than the second voltage range of the pair of
first-level signals, wherein
the input buffer means includes a first transistor having a source and
drain and a second transistor having a source and drain,
the source of the first transistor and the source of the second transistor
is coupled to a first power supply
the drain of the first transistor and the drain of the second transistor is
coupled to a second power supply by way of
a pair of buffered signals having a predetermined amplitude is output via
connection nodes from the drain of the first transistor and the drain of
the second transistor to the amplifier circuit.
2. The level conversion circuit as claimed in claim 1, wherein the second
voltage range is situated above the low-potential power supply voltage.
3. The level conversion circuit as claimed in claim 1, wherein the input
buffer circuit comprises a differential amplifier having a pair of MOS
transistors.
4. The level conversion circuit as claimed in claim 1, wherein the input
buffer circuit comprises:
a first P-channel MOS transistor having a source coupled to a first power
supply line of the high-potential power supply voltage via a first
resistance network, a gate receiving one of the pair of first-level
signals, and a drain coupled to a second power supply line of the
low-potential power supply voltage via a second resistance network; and
a second P-channel MOS transistor having a source coupled to the first
power supply line via the first resistance network, a gate receiving the
other one of the pair of the first-level signals, and a drain coupled to
the second power supply line via the second resistance network.
5. A level conversion circuit for converting a pair of first-level signals
into a pair of second-level signals, said level conversion circuit being
supplied with a high-potential power supply voltage and a low-potential
power supply voltage, said level conversion circuit comprising:
input buffer means for converting the pair of first-level signals into a
pair of buffered signals which vary within a first voltage range situated
below a second voltage range within which the pair of first-level signals
vary; and
an amplifier circuit comprising a plurality of CMOS differential amplifier
circuits cascaded, the amplifier circuit converting the pair of buffered
signals into the pair of second-level signals varying within a third
voltage range broader than the second voltage range of the pair of
first-level signals,
wherein the input buffer circuit comprises:
a first P-channel MOS transistor having a source coupled to a first power
supply line of the high-potential power supply voltage via a first
resistance network, a gate receiving one of the pair of first-level
signals, and a drain coupled to a second power supply line of the
low-potential power supply voltage via a second resistance network; and
a second P-channel MOS transistor having a source coupled to the first
power supply line via the first resistance network, a gate receiving the
other one of the pair of the first-level signals, and a drain coupled to
the second power supply line via the second resistance network, and
wherein the first resistance network comprises a first resistance element
connected between the first power supply line and the sources of the first
and second P-channel MOS transistors; and
wherein the second resistance network comprises:
a first resistance element having a first end connected to the drain of the
first P-channel MOS transistor, and a second end;
a second resistance element having a third end connected to the drain of
the second P-channel MOS transistor, and a fourth end; and
a third resistance element having a fifth end connected to the second and
fourth ends, and a sixth end connected to the second power supply line,
the pair of buffered signals being output via the drains of the first and
second P-channel MOS transistors.
6. A level conversion circuit for converting a pair of first-level signals
into a pair of second-level signals, said level conversion circuit being
supplied with a high-potential power supply voltage and a low-potential
power supply voltage, said level conversion circuit comprising:
input buffer means for converting the pair of first-level signals into a
pair of buffered signals which vary within a first voltage range situated
below a second voltage range within which the pair of first-level signals
vary; and
an amplifier circuit comprising a plurality of CMOS differential amplifier
circuits cascaded, the amplifier circuit converting the pair of buffered
signals into the pair of second-level signals varying within a third
voltage range broader than the second voltage range of the pair of
first-level signals, wherein an ith CMOS differential amplifier circuit
among the plurality of CMOS differential amplifier circuits comprises:
a first P-channel MOS transistor having a source connected to a first power
supply line of the high-potential power supply voltage via a resistance
element, a drain via which a first output signal is output to an (i+1)th
CMOS differential amplifier circuit, and a gate receiving a first input
signal from an (i-1)th CMOS differential amplifier circuit;
a second P-channel MOS transistor having a source connected to the first
power supply line of the high-potential power supply voltage via the
resistance element, a drain via which a second output signal is output to
the (i+1)th CMOS differential amplifier circuit;
a first N-channel MOS transistor having a drain connected to the drain of
the first P-channel MOS transistor, a source coupled to a second power
supply line of the low-potential power supply voltage, and a gate
connected to the drain of the first N-channel MOS transistor; and
a second N-channel MOS transistor having a drain connected to the drain of
the second P-channel MOS transistor, a source coupled to the second power
supply line, and a gate connected to the drain of the second N-channel MOS
transistor.
7. The level conversion circuit as claimed in claim 6, further comprising
discharging means for discharging the drains of the first and second
P-channel MOS transistors in response to the first and second input
signals.
8. The level conversion circuit as claimed in claim 6, further comprising:
a third N-channel MOS transistor having a drain connected to the gate and
drain of the first N-channel MOS transistor, a source connected to the
source of the first N-channel MOS transistor, and a gate receiving the
first input signal; and
a fourth N-channel MOS transistor having a drain connected to the gate and
drain of the second N-channel MOS transistor, a source connected to the
source of the second N-channel MOS transistor, and a gate receiving the
second input signal.
9. A level conversion circuit for converting a pair of first-level signals
into a pair of second-level signals, said level conversion circuit being
supplied with a high-potential power supply voltage and a low-potential
power supply voltage, said level conversion circuit comprising:
input buffer means for converting the pair of first-level signals into a
pair of buffered signals which vary within a first voltage range situated
below a second voltage range within which the pair of first-level signals
vary; and
an amplifier circuit comprising a plurality of CMOS differential amplifier
circuits cascaded, the amplifier circuit converting the pair of buffered
signals into the pair of second-level signals varying within a third
voltage range broader than the second voltage range of the pair of
first-level signals, wherein one of the plurality of CMOS differential
amplifier circuits comprises:
a first P-channel MOS transistor having a source connected to a first power
supply line of the high-potential power supply voltage via a resistance
element, a drain via which a first output signal is output to an (i+1)th
CMOS differential amplifier circuit, and a gate receiving a first input
signal from an (i-1)th CMOS differential amplifier circuit;
a second P-channel MOS transistor having a source connected to the first
power supply line of the high-potential power supply voltage via the
resistance element, a drain via which a second output signal is output to
the (i+1)th CMOS differential amplifier circuit, and a gate receiving a
second input signal from the (i-1)th CMOS differential amplifier circuit;
a first N-channel MOS transistor having a drain connected to the drain of
the first P-channel MOS transistor, a source coupled to a second power
supply line of the low-potential power supply voltage, and a gate
connected to the drain of the first N-channel MOS transistor;
a second N-channel MOS transistor having a drain connected to the drain of
the second P-channel MOS transistor, a source coupled to the second power
supply line, and a gate connected to the drain of the second N-channel MOS
transistor; and
discharging means for discharging the drains of the first and second
P-channel MOS transistors in response to the second and first output
signals.
10. The level conversion circuit as claimed in claim 9, wherein said
discharging means comprises:
a third N-channel MOS transistor having a drain connected to the gate and
drain of the first N-channel MOS transistor, a source connected to the
source of the first N-channel MOS transistor, and a gate receiving the
second output signal; and
a fourth N-channel MOS transistor having a drain connected to the gate and
drain of the second N-channel MOS transistor, a source connected to the
source of the second N-channel MOS transistor, and a gate receiving the
first output signal.
11. A level conversion circuit for converting a pair of first-level signals
into a pair of second-level signals, said level conversion circuit being
supplied with a high-potential power supply voltage and a low-potential
power supply voltage, said level conversion circuit comprising:
input buffer means for converting the pair of first-level signals into a
pair of buffered signals which vary within a first voltage range situated
below a second voltage range within which the pair of first-level signals
vary;
an amplifier circuit comprising a plurality of CMOS differential amplifier
circuits cascaded, the amplifier circuit converting the pair of buffered
signals into the pair of second-level signals varying within a third
voltage range broader than the second voltage range of the pair of
first-level signals; and
output buffer means for converting the pair of second-level signals into an
output signal.
12. The level conversion circuit as claimed in claim 11, wherein the output
buffer means comprises a CMOS inverter.
13. The level conversion circuit as claimed in claim 1, wherein the pair of
first-level signals is a pair of ECL-level signals, and the pair of
second-level signals is a pair of CMOS-level signals.
Description
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention generally relates to an ECL-CMOS (Emitter-Coupled
Logic/Complementary Metal Oxide Semiconductor) level conversion circuit
for converting an ECL-level signal into a CMOS-level signal, and more
particularly to an ECL-CMOS level conversion circuit including CMOS
circuits.
2. Description of the Prior Art
Recently the operating speed of integrated circuits has been increased, and
accordingly an interface circuitry operating with low-amplitude signals
like those of ECL has been required. Particularly, there are recent
development trends to design circuit configurations in which a logic
circuit is formed by a CMOS circuit of low power consumption and high
integration density and an interface between the logic circuit and an
external circuit is established by a level conversion circuit.
Various ECL-CMOS or CMOS-ECL level conversion circuits using Bi-CMOS
(Bipolar/CMOS) circuits have been proposed (for example, Japanese
Laid-Open Patent Application No. 3-283813). An ECL interface is capable of
transferring data at a speed of 100 MHz or higher.
An ECL-CMOS level conversion circuit of a CMOS configuration is known (for
example, Japanese Laid-Open Patent Application No. 63-15519). Normally,
the design of CMOS circuits is more complicated than that of Bi-CMOS
circuits because the operation characteristics of CMOS circuits are less
stable than those of Bi-CMOS circuits. Further, the operating speed of
CMOS circuits are lower than that of Bi-CMOS circuits. On the other hand,
CMOS circuits can be formed on a chip by a production process simpler than
that of Bi-CMOS circuits.
Most recently proposed ECL-CMOS level conversion circuits have the CMOS
configuration. However, since the CMOS circuits can be easily formed on a
chip, it is desired to provide an ECL-CMOS level conversion circuit of the
CMOS type capable of stably operating at a high speed.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide an ECL-CMOS level
conversion circuit of a CMOS configuration capable of stably operating at
a high speed.
This object of the present invention is achieved by a level conversion
circuit for converting a pair of first-level signals into a pair of
second-level signals, the level conversion circuit being supplied with a
high-potential power supply voltage and a low-potential power supply
voltage, the level conversion circuit comprising: input buffer for
converting the pair of first-level signals into a pair of buffered signals
which vary within a first voltage range situated below a second voltage
range within which the pair of first-level signals vary; and an amplifier
circuit comprising a plurality of CMOS differential amplifier circuits
cascaded, the amplifier circuit converting the pair of buffered signals
into the pair of second-level signals varying within a third voltage range
broader than the second voltage range of the pair of first-level signals.
BRIEF DESCRIPTION OF THE DRAWINGS
Other objects, features and advantages of the present invention will become
more apparent from the following detailed description when read in
conjunction with the accompanying drawings, in which:
FIG. 1 is a circuit diagram of a conventional ECL-CMOS level conversion
circuit of a CMOS type;
FIG. 2 is a block diagram of the principle of an ECL-CMOS level conversion
circuit according to the present invention;
FIG. 3 is a circuit diagram of an input buffer circuit shown in FIG. 2;
FIG. 4 is a circuit diagram of a differential amplifier circuit shown in
FIG. 2;
FIG. 5 is a circuit diagram of a differential amplifier circuit located at
the final stage immediately before an output inverter circuit;
FIG. 6 is a circuit diagram of the overall ECL-CMOS level conversion
circuit shown in FIG. 2;
FIG. 7 is a graph of the characteristics of the input buffer circuit shown
in FIG. 3 and a first-stage differential amplifier circuit shown in FIG.
1;
FIG. 8 is a graph of the characteristics of the final-stage differential
amplifier circuit shown in FIGS. 1 and 6;
FIG. 9 is a graph of the characteristics of CMOS-level output signals
output by the output inverter circuits shown in FIGS. 1 and 6;
FIG. 10 is a graph of the characteristics of the final-stage differential
amplifier circuits shown in FIGS. 5 and 6;
FIG. 11 is a graph of the characteristics of the CMOS-level output signals
obtained when the final-stage differential amplifier circuits shown in
FIGS. 5 and 6 are used; and
FIG. 12 is a block diagram of an application of the present invention.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
FIG. 1 is a circuit diagram of a conventional ECL-CMOS level conversion
circuit of the CMOS type. The ECL-CMOS level conversion circuit shown in
FIG. 1 is made up of three cascaded differential amplifier circuits 13-1,
13-2 and 13-3, and an output inverter circuit 5. Each of the differential
amplifier circuits 13-1, 13-2 and 13-3 includes two P-channel MOS
transistors (PMOS transistors) TP1 and TP2, two N-channel MOS transistors
(NMOS transistors) TN1 and TN2, and a resistor R5. Complementary ECL-level
input signals IN and IN# are applied to the gates of the PMOS transistors
TP1 and TP2 of the circuit 13-1, respectively. The drains of the PMOS
transistors TP1 and TP2 of the circuit 13-1 are connected to the gates of
the PMOS transistors TP1 and TP2 of the circuit 13-2, respectively. The
output inverter circuit 5 is formed with a CMOS inverter consisting of a
PMOS transistor TP5 and an NMOS transistor TN5. A CMOS-level output signal
is available at a connection node at which the drains of the transistors
TP5 and TN5 are connected together. A high-potential power supply voltage
VDD of 0V and a low-potential power supply voltage VSS of -3.3V are
applied to the circuit shown in FIG. 1.
The reason why a plurality of amplifier circuits are cascaded is that if a
single amplifier stage is employed, it will take a long time for the
CMOS-level signal to switch between high and low levels in response to a
switching of the ECL-level input signal. Therefore, the level conversion
circuit cannot operate at high speed, because the ECL levels are quite
different from CMOS levels. By using a plurality of amplifier circuits, it
becomes possible to reduce the level difference between the input and
output of each of the amplifiers.
As will be described later, the ECL-CMOS level conversion circuit shown in
FIG. 1 does not have sharp leading and trailing edges in the waveform of
the CMOS-level signal.
The present invention is intended to provide an improved ECL-CMOS level
conversion circuit of the CMOS type.
FIG. 2 is a block diagram of the principle of the present invention. An
ECL-CMOS level conversion circuit of the CMOS type shown in FIG. 2
includes an input buffer circuit 1, n differential amplifier circuits 3-1
through 3-n where n is an integer, and the output buffer circuit 5. One
possibility for the configuration in FIG. 2 (n=3)is to add circuit 1 to
the configuration of FIG. 1. 10 The input buffer circuit 1 receives the
ECL-level signals IN and IN#, and outputs level-converted output signals a
and b to the first-stage differential amplifier circuit 3-1. The output
signals a and b have levels lower than those of the ECL-level signals IN
and IN# and higher than the low-potential power supply voltage VSS. For
example, the ECL-level signals IN and IN# vary between -1.8V and -0.9V,
and the low-potential power supply voltage VSS is -3.3V. In this case, the
output signals a and b of the input buffer circuit 1 vary between
approximately -3.0V and -2.6V. This voltage range of the output signals a
and b can be more easily processed by the first-stage differential
amplifier circuit 3-1 of the CMOS type than the voltage range of the
ECL-level input signals IN and IN#.
More particularly, the ECL-level signals IN and IN# are too high to enable
amplification of these signals by the PMOS transistors TP1 and TP2 of the
first-stage circuit 3-1. Further, it is desired that the output signals of
the first-stage circuit 3-1 vary within a voltage range as small as
possible in order to gradually amplify the amplitudes of the signals by
means of the differential amplifier circuits 3-1 through 3-n. From these
viewpoints, the ECL-level input signals IN and IN# are shifted to a
voltage range lower than the ECL levels and slightly higher than the
low-potential power supply voltage VSS. Hence, the PMOS transistors TP1
and TP2 can be made to operate in an approximately saturated state.
FIG. 3 is a circuit diagram of the input buffer circuit 1, which is made up
of two PMOS transistors TP1 and TP2, and four resistors R1, R2, R3 and R4.
The ECL-level input signals IN and IN# are applied to the gates of the
PMOS transistors TP1 and TP2, respectively. A VDD power supply line is
coupled to the sources of the PMOS transistors TP1 and TP2 via the
resistor R3. The drains of the PMOS transistors TP1 and TP2 are connected
to one end of the resistor R4 via the resistors R1 and R2, respectively.
The other end of the resistor R4 is connected to a VSS power supply line.
The output signals a and b are output from the drains of the PMOS
transistors TP1 and TP2, respectively.
It is preferable that each of the differential amplifier circuits 3-1
through 3-n has a configuration shown in FIG. 4, in which the circuit
configuration of only the circuit 3-1 is illustrated for the sake of
simplicity. In FIG. 4, parts that are the same as those shown in the
previously described figures are given the same reference numbers as
previously. The differential amplifier circuit 3-1 shown in FIG. 4 is
configured by adding NMOS transistors TN3 and TN4 to the circuit
configuration shown in FIG. 1.
More particularly, the gate of the NMOS transistor TN3 receives the output
signal a of the input buffer circuit 1, and the gate of the NMOS
transistor TN4 receives the output signal b thereof. The drain of the NMOS
transistor TN3 is connected to the drain of the PMOS transistor TP3 and
the drain and gate of the NMOS transistor TN1. Similarly, the drain of the
NMOS transistor TN4 is connected to the drain of the PMOS transistor TP4
and the drain and gate of the NMOS transistor TN2. The sources of the NMOS
transistors TN3 and TN4 are connected to the sources of the NMOS
transistors TN1 and TN2, respectively.
The NMOS transistors TN3 and TN4 facilitate a discharging operation. The
transistor TN3 immediately responds to a change of the signal a before a
change in the state of the associated PMOS transistor TP3. Similarly, the
transistor TN4 immediately responds to a change of the signal b before a
change in the state of the associated PMOS transistor TP4. In this manner,
the nodes from which the output signals are drawn can be discharged more
rapidly than the nodes in the configuration shown in FIG. 1.
It is possible to reduce the size (gate width) of the NMOS transistors TN1
and TN2 because the NMOS transistors TN3 and TN4 are employed. Hence, the
impedance of the NMOS transistors TN1 and TN2 is increased, whereby the
speed of charging that is performed after the transistors TN3 and TN4 are
turned OFF can be slightly increased.
It is possible to configure the final-stage differential amplifier circuit
3-n as shown in FIG. 5, in which parts that are the same as those shown in
the previously described figures are given the same reference numbers as
previously. The output signals [1] and [2] of the (n-1)th differential
amplifier circuit are applied to the gates of the PMOS transistors TP3 and
TP4. The gate of the NMOS transistor TN3 is connected to the drain of the
PMOS transistor TP4, and the gate of the NMOS transistor TN4 is connected
to the drain of the PMOS transistor TP3.
When an output signal e of the final-stage circuit 3-n is switched towards
the VDD level and an output signal f thereof is switched towards the VSS
level, the potential of the gate of the NMOS transistor TN4 is increased,
and the potential of the gate of the NMOS transistor TN3 is decreased. As
the gate of the NMOS transistor TN4 is increased, the state of the
transistor TN4 is changed towards ON, and the potential of the drain
thereof is decreased. This decrease in the drain potential of the
transistor TN4 causes the transistor TN3 to be changed towards OFF. As a
result, the drain potential of the transistor TN3 is increased, and hence
the state of the transistor TN4 is caused to further shift to the ON
state. In this manner, the switching operation of the final-stage circuit
3-n can be improved.
FIG. 6 is a circuit diagram of the overall ECL-CMOS level conversion
circuit having the circuit configurations shown in FIGS. 3 and 4. The
ECL-CMOS level conversion circuit converts the ECL-level input signals IN
and IN# varying between -1.8V and -0.9V to the CMOS-level signal varying
between -3.0V and 0V. Instead of the final-stage differential amplifier
circuit 3-3 shown in FIG. 6, it is possible to use the circuit
configuration shown in FIG. 5.
A description will now be given, with reference to FIGS. 7, 8 and 9, of the
characteristics of the circuit shown in FIGS. 1 and 6 obtained by a
computer simulation. In the simulation, the values of the circuit
parameters were selected as follows.
R1-R5: 1 k.OMEGA.
W of TP1, TP2 of circuit 1: 70 .mu.m
L of TP1, TP2 of circuit 1: 0.5 .mu.m
W of TP3, TP4 of circuit 3-1: 50 .mu.m
L of TP3, TP4 of circuit 3-1: 0.5 .mu.m
W of TP3, TP4 of circuits 3-2, 3-3: 40 .mu.m
L of TP3, TP4 of circuits 3-2, 3-3: 0.5 .mu.m
W of TN1, TN2 of circuits 3-1, 3-2, 3-3: 10 .mu.m
L of TN1, TN2 of circuits 3-1, 3-2, 3-3: 0.5 .mu.m
W of TN3, TN4 of circuits 3-1, 3-2, 3-3: 5 .mu.m
L of TN3, TN4 of circuits 3-1, 3-2, 3-3: 0.5 .mu.m
W of TP5, TN5 of circuit 5: 30 .mu.m
L of TP5, TN5 of circuit 5: 0.5 .mu.m
W: channel width
L: channel length
FIG. 7 shows the output signals a and b of the input buffer circuit 1 shown
in FIGS. 3 and 6 according to the embodiment of the present invention, and
the output signals h and i of the first-stage differential amplifier
circuit 13-1 shown in FIG. 1 that directly receives the ECL-level input
signals IN and IN#. In FIG. 7, the horizontal axis denotes the time
(nanoseconds: N), and the vertical axis denotes the voltage (V). It can be
seen from FIG. 7 that the output signals a and b of the input buffer
circuit 1 have voltage levels lower than those of the output signals h and
i of the first-stage differential amplifier circuit 13-1 shown in FIG. 1
and leading and trailing edges sharper than those of the output signals h
and i.
FIG. 8 shows the output signals c and d of the final-stage differential
amplifier circuit 3-3 shown in FIG. 6 according to the embodiment of the
present invention, and the output signals j and k thereof in the
configuration shown in FIG. 1. It can be seen from FIG. 8 that the output
signals c and d of the final-stage differential amplifier circuit 3-3
shown in FIG. 6 vary in a voltage range broader than that of the output
signals j and k. Particularly, the logical low level of the output signals
c and d is much lower than that of the output signals j and k, and is very
close to the low-potential power supply voltage VDD. Hence, the
final-stage differential amplifier circuit 3-3 shown in FIG. 6 can operate
more stably than the final-stage differential amplifier circuit 13-3 shown
in FIG. 1.
FIG. 9 shows the CMOS-level output signal OUT of the output inverter
circuit 5 shown in FIG. 6, and the CMOS-level output signal OUT of that
shown in FIG. 1. It can be seen from FIG. 9 that the ECL-CMOS level
conversion circuit shown in FIG. 6 has leading and trailing edges sharper
than those of the signal OUT shown in FIG. 1 and hence can operate more
stably and at higher speed than the ECL-CMOS level conversion circuit
shown in FIG. 6.
It is possible to set one of the two differential signals to a reference
voltage equal to, for example, -1.3V.
FIG. 10 shows the output signals c and d of 10 the final-stage differential
amplifier circuit 3-3 shown in FIG. 6, and the output signals e and f of
the final-stage differential amplifier circuit 3-3 shown in FIG. 5. The
output signals e and f of the final-stage differential amplifier circuit
3-3 shown in FIG. 5 fall more rapidly than the output signals c and d, and
the circuit 3-3 shown in FIG. 5 can operate at a speed faster than the
circuit 3-3 shown in FIG. 6.
FIG. 11 shows the CMOS-level output signal OUT of the output inverter
circuit 5 shown in FIG. 6, and the CMOS-level output signal OUT obtained
when the final-stage differential amplifier circuit 3-3 shown in FIG. 5 is
used. It can be seen from FIG. 11 that the ECL-CMOS level conversion
circuit employing the final-stage circuit 3-3 shown in FIG. 5 has leading
and trailing edges sharper than those of the signal OUT shown in FIG. 6
and hence can operate more stably and at higher speed than the ECL-CMOS
level conversion circuit shown in FIG. 6.
FIG. 12 shows two chips A and B. The chip A includes a CMOS circuit area
and a plurality of ECL-CMOS level conversion circuits according to the
present invention. The chip B includes a CMOS circuit area and a plurality
of CMOS-ECL level conversion circuits. In practice, the chip A includes
CMOS-ECL level conversion circuits, and the chip B includes ECL-CMOS level
conversion circuits.
The present invention is not limited to the specifically disclosed
embodiments, and variations and modifications may be made without
departing from the scope of the present invention.
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